This communications presents a statistical evaluation of the calibration ac
curacy of an airborne scatterometer system. The internal and external calib
rations were conducted over a two-year time period. It was shown that the a
bsolute calibration accuracy of the Helsinki University of Technology airbo
rne scatterometer (HUTSCAT) is better than 0.6 dB with 90% confidence. The
techniques are generally applicable to stable airborne remote-sensing radar
s.